The present invention relates to a manufacturing device and a method for manufacturing an electromagnetic element for an electrical machine, which comprises a curved stator lamination.
For stators of electrical machines designed to be used as high-performance generators for motor vehicles, it has already been provided by WO 01/54254 A1 to join strip-shaped laminations and thereby produce an essentially parallelepipedal stator lamination, to curve the stator lamination into a hollow cylindrical shape, and to bond the two ends with each other, e.g., via welding. The better that the ends can be connected in a form-fit manner, the better the overall results are. A further aim is to attain the greatest possible roundness of the thusly-formed stator in its stator bore. The better the roundness is, the smaller the air gap of the machine can be designed to be, the better the material utilization and power output are, and the quieter the electrical machine is.
To improve the roundness, it was provided in EP 1 109 286 A2 to curve both ends of the parallelepipedal stator lamination at the start of manufacture such that the stator lamination takes on a predetermined curvature in this region. Only then is the entire stator lamination curved into the hollow cylindrical shape by placing the stator lamination around a cylindrical bending mandrel and applying pressure on it using a bending roller that acts on the external side of the stator lamination. In the flat state, the two ends are still freely accessible and can be shaped very easily such that, after the stator lamination is curved into a round shape, the pre-curved ends face each other and only need to be joined. Good roundness of the stator can therefore be attained. If, however, a core winding with at least one winding overhang is wound and joined in the stator lamination, and at least one slot is provided on one of its ends for accommodating the winding overhang, this end cannot be curved in advance, since doing so would close the slots in this region, thereby making it impossible to insert the winding overhang in the predetermined slot.
In addition, a large number of requirements on the manufacture of an electromagnetic element must be fulfilled. For example, when unfavorable winding types and coil shapes are used, the laminations expand in an irregular manner at the end faces and in the middle of the stator lamination, which results in an uneven gap width between the ends of the stator lamination to be joined. In fact, the gap width is that much more uneven the thinner the laminations are and the bulkier the winding overhangs are.
When the flexural behavior of individual laminations is not uniform, this also results in problems in joining the overhang coil. In some cases, stator laminations with overhang coils must be bent in stages, in order to make it possible to join the overhang coil; this procedure results in considerable out-of-roundness.